The present invention relates to a large, typically cylindrical, plastic body and a method and apparatus for making same.
Molding of large plastic objects presents many difficulties. When injection molding is used, very high pressures in excess of 5,000 pounds per square inch are required. These pressures create difficulties because the molds must be massively constructed in order to avoid the danger of mold failure. The massive construction of molds adds to the expense of the molds and results in molds which are difficult to handle.
It is therefore desirable to be able to mold large plastic objects at lower pressures and by so doing reduce the stress on the molds. This allows molds to be formed of lighter construction and reduces the difficulties in the manufacturing and handling of the molds.
Therefore a primary object of the present invention is the provision of an improved method and apparatus for making a large cylindrical plastic body.
A further object of the present invention is the provision of a method and apparatus for making a large plastic body having an elongated metal tube extending along its axial length.
A further object of the present invention is the provision of a method and apparatus for making a large plastic body which has a length up to greater than 20 feet and a cross-sectional area up to greater than 200 square inches.
A further object of the present invention is the provision of an improved apparatus and method for molding a plastic body wherein the molding operation is accomplished at very low pressures of less than 1,000 PSI.
A further object of the present invention is the provision of an apparatus and method for making a body, typically cylindrical, which is efficient in operation, simple in construction, and durable in use.